Embodiments generally relate to a medical telemetry system, and more particularly to a convertible antenna assembly configured for use with a tablet-based medical telemetry system.
Numerous medical devices exist today, including but not limited to electrocardiographs (“ECGs”), electroencephalographs (“EEGs”), squid magnetometers, implantable pacemakers, implantable cardioverter-defibrillators (“ICDs”), neurostimulators, electrophysiology (“EP”) mapping and radio frequency (“RF”) ablation systems, and the like (hereafter generally “implantable medical devices” or “IMDs”). IMDs commonly employ one or more leads with electrodes that either receive or deliver voltage, current or other electromagnetic pulses (generally “energy”) from or to an organ or tissue (collectively hereafter “tissue”) for diagnostic or therapeutic purposes.
Various IMDs are programmed and monitored by an external programmer or external home-based patient care system. For example, a patient may have an IMD that communicates with a base station within the patient's home or a programmer that is used by physicians to change settings within the IMD and/or retrieve data from the IMD. The base station or external programmer device receives data from the IMD about the patient's physiological state. For example, the IMD may transmit stored data or sensed physiological parameters to the base station. Based on the received data, the base station or external programmer device may adjust operating parameters for the IMD.
Conventional external programmers and base stations employ near-field RF data communication techniques that facilitate communication between the IMD and a telemetry wand that is operatively connected to the base station. Typically, the wand of the base station or programmer is placed in close proximity to the IMD in order to establish a communication link. More recently, however, IMD telemetry assemblies have been proposed that employ far-field RF data communication techniques that do not require close proximity between the IMD and the wand of the programmer or base station. Further, some systems do not even include a separate and distinct telemetry wand, and the RF circuitry and antenna are embedded within the housing of the external programmer device or home base station.
Many telemetry systems communicate with IMDs using the Medical Implant Communication Service (MICS) band. Generally, the MICS band is an allocated frequency between 402-405 MHz. The MICS band enables a short-range, wireless link to be maintained between low-power implanted IMDs and an external programmer or base station.
Recently, it has been proposed to size and shape the external programmer device similar to a small notebook computer or tablet (such as an iPad® device offered by Apple). However, difficulties exist in connection with implementing small size external programmers. For example, the RF performance of the telemetry system within the programmer device may be affected as the housing of the programmer becomes smaller and the programmer is portable and handled more frequently by the physician or other user.
As one example of a size-related challenge, it is desirable for a quarter-wave monopole antenna that operates in the 402-405 MHz MICS band, to be about 7″ long, and to be mounted above a ground plane within the external programmer. However, physicians and other users may find such an antenna to be obtrusive, distracting, or simply unwieldy. The antenna length and location limit the amount of size reduction that can be achieved in the overall form-factor (size envelope) for the portable, compact tablet-type programmer device or base station.
Additionally, incorporating a monopole antenna within a tablet-type device poses further drawbacks. The embedded antenna exhibits certain tuning characteristics that affect the antenna performance. A user grasping the exterior housing of the tablet-type programmer device may change the tuning characteristics of the antenna and cause the antenna to become detuned. The degree and manner by which the antenna is “detuned” is dependent, at least in part, upon where the user grasps the antenna.
Further, signal attenuation become a greater concern as the programmer size is reduced. Signals that are transmitted in the RF field to/from the antenna of the programmer device may be attenuated by the user, when the user places his/her hands on the housing of the tablet-type programmer. The RF field communications signals may be attenuated by the tablet housing or other conductive materials proximate to the antenna. Miniaturization of the tablet may not provide enough space for a properly-sized conventional antenna assembly and may cause the conventional antenna assembly to be inadequately shielded from the electronics on a motherboard of the tablet programmer device.
Also, with portability, the user may hold the tablet programmer in various positions and orientations with respect to the patient while in use. As the table programmer is moved or re-oriented, the polarization between the tablet antenna and the IMD antenna may become mismatched. Further, there may be nulls in the transmission/reception pattern generated by conventional antenna assemblies, such that the when the IMD is located in a null, a communications link cannot be maintained between the IMD and the programmer device.